Vibrational relaxation dynamics in I-2(-)(CO2)(4) clusters are monitored by femtosecond stimulated emission pumping in conjunction with femtosecond photoelectron spectroscopy. Femtosecond pump and tunable dump pulses coherently excite the I-2(-) within the cluster with vibrational energies ranging from 0.57 to 0.86 eV; the subsequent dynamics are monitored via the time-dependent photoelectron spectrum, and are compared to those resulting from excitation of bare I-2(-). Two observables are used to follow the vibrational relaxation from the vibrationally excited I-2(-) to the surrounding solvent molecules. From 0 to 4 ps, relaxation is apparent through a time-dependent increase in the oscillation which is monitored at its inner turning point. At longer times, out to similar to100 ps, shifts in the photoelectron spectra are used to determine the vibrational energy content of the I-2(-). Indirect evidence is presented for early rapid energy loss during the first half-oscillation of the wave packet across the potential.